1. Field of the Invention
The present invention relates to a detector of a liquid consumption condition that can detect a consumption condition of a liquid such as an ink, by detecting changes in an acoustic impedance, particularly by detecting changes in a resonance frequency.
2. Description of the Related Art
In an ink jet recording apparatus, an ink jet recording head having: a pressure generating means that can pressurize a pressure generating chamber; and a nozzle that can jet pressurized ink as an ink drop, is mounted on a carriage. In the ink jet recording apparatus, ink in an ink tank continues to be fed to the recording head via a flow path, so as to permit continuous printing. The ink tank is generally structured as a removable cartridge that can be simply exchanged by a user when the ink is consumed.
Conventionally, as an ink consumption control method of an ink cartridge, a method for totalizing the number of ink drops jetted by the recording head and the ink amount sucked at the maintenance step by means of some software and controlling the ink consumption from calculation; and a method for attaching electrodes for detecting a liquid level to the ink cartridge, detecting the point of time when the ink is actually consumed by a predetermined amount, thereby controlling the ink consumption; are known.
The method for totalizing the number of jetted ink drops and the sucked ink amount by the software and controlling the ink consumption from calculation has an advantage in cost, because the method needs no special detector. However, in the method, some errors may be caused by difference of printing manners that can be selected by the user. In addition, larger errors may be generated when the same cartridge is refitted. Furthermore, pressure in the ink cartridge and ink viscosity may be varied with a use environment (for example, extremely high or low room temperature), or an elapsed time after opening the ink cartridge, so that unnegligible errors may be caused between the ink consumption from calculation and the actual consumption.
On the other hand, the method of controlling the point of time of ink consumption by the electrodes can detect the actual amount of ink consumption at a certain point, so that it can control the residual quantity of ink with high reliability. However, the ink has to be conductive so as to detect the ink level, accordingly the kind of ink to be used (detected) is limited. Further, a problem arises that the liquid tight structure between the electrodes and the ink cartridge is complicated. Furthermore, as a material of the electrodes, a noble metal which is enough conductive and highly corrosion-resistant is ordinarily used, so that a problem also arises that manufacturing cost of an ink cartridge is increased. Furthermore, two electrodes must be mounted, so that many manufacturing steps are required and the manufacturing cost is more increased.
An object of the present invention is to provide a detector of liquid consumption condition that can effectively make good use of the detection of the liquid consumption condition.